AES E-Library

An Enhanced Encoder for the MPEG-4 ALS Lossless Coding Standard

MPEG-4 ALS is a lossless coding standard for audio signals based on time-domain prediction, and it was officially published in March 2006. Enhanced encoder algorithms and implementation examples of the MPEG-4 ALS are shown in this paper. To reduce the computational complexity of the encoder, new algorithms have been developed for the multi-channel prediction coding (MCC) tool, the long-term prediction (LTP) tool, and the hierarchical block switching (BS) tool. In addition, processing speed has been enhanced by means of software optimization, including assembler codes. As a result of these improvements, the software provides maximally 10 times faster encoding speed than that of the MPEG reference software and becomes more useful for various practical applications.